<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>07_DOM操作 2</title>
</head>
<body>
    <input type="text" id="i1">
    <input type="text" id="i2">
    <button onclick="f()">anniu</button>
    <hr>
    <h4>标题<span id="ss"></span></h4>
    <button onclick="f1()">button</button>
<script>
  function f(){
    var a = parseFloat(i1.value);
    var b = parseFloat(i2.value);
    var c = a+b;
    console.log(c)
  }
  function f1(){
    var ss = document.getElementById("ss");
    ss.innerHTML = "hello world";
  }
</script>
</body>
</html>